Several million people have to go to the emergency rooms every year because polluted air has triggered an asthma attack on them. Now researchers have for the first time estimated how many people are affected by it. According to the calculations, the inhalation of ozone, nitrogen dioxide and particulate matter annually leads to nine to 33 million asthma emergencies.

"Millions of people come to emergency rooms with asthma because they've inhaled dirty air," says study leader Susan Anenberg of the Milken Institute School of Public Health. "Our findings suggest that clean air measures could reduce the global burden of asthma and significantly contribute to respiratory health."

For their study, now published in the journal Envrionmental Health Perspective, the researchers collected data from four areas, which they then combined. In detail, they used

  • Satellite data on global air pollution,
  • Numbers of the incidence of asthma in the population,
  • Numbers of frequency of emergency room visits as well
  • Figures how much different substances in the air increase the risk of asthma.

All information came from 2015.

Gases irritate the respiratory tract

According to the calculations, ozone alone is responsible for between nine and 23 million emergency room asthma attacks every year, which is 8 to 20 percent of all asthma emergencies worldwide. Ozone is a specific form of oxygen that is created, inter alia, by the interaction of exhaust gases and sunlight. The gas irritates the respiratory tract.

Five to ten million asthma emergencies (about 4 to 9 percent of all asthma cases) attributed the researchers to particulate matter . They only consider ultrafine particles (PM2.5), which due to their size can penetrate into the small bronchi and alveoli.

As a third substance, the researchers analyzed the effects of nitrogen dioxide , which is currently being discussed due to diesel driving bans. The irritant gas was calculated to cause between 0.4 and 0.5 million asthma casualties in 2015 - equivalent to 0.4 percent of all those affected. Nitrogen oxides are formed when coal, oil, gas or wood are burnt. In cities, a large part of the traffic.

Between 12 and 30 percent of all asthma emergencies

Together, polluted air is responsible for between 12 and 30 percent of all asthma emergencies. Among other things, the large range of all numbers can be explained by the fact that the researchers had different values ​​from different studies, especially with regard to the extent of the asthma risk from the substances. They took this into account in their results.

It is also important that not the complete air pollution is due to the behavior of the people and thus avoidable. Fine dust, for example, is also produced in nature; it can penetrate the body in the form of dust or sea salt, for example. Thunderstorms with their lightning contribute to the ozone load.

According to the calculations, only 37 percent of the asthma attacks caused by ozone are completely human-based. With fine dust, the influence of humans - and thus the number of avoidable cases - is significantly higher at 73 percent.

Nitrogen dioxide: low-key estimate

The number of asthma cases by nitrogen dioxide is probably still underestimated in the calculation, the researchers write. In their data, they could not take into account that some people live very close to large streets and there are exposed to about three times higher concentration than people who have their home less than half a kilometer away.

On the other hand, it is also likely that some sufferers appear in both the particulate matter and the nitrogen category because a combination of both has triggered the disease. Particulate matter and nitrogen oxides are closely linked: nitrogen dioxide contributes to particulate matter pollution. In addition, the tiny particulate matter particles also form during transport but also due to the abrasion of tires and brake linings.

The current study gives a first impression of how much air pollution affects the asthma rate. However, they still rely on many estimates and uncertainties, the researchers write. They call for the scientific methods and underlying data to be further developed in future studies. This is definitely important: About 95 percent of the world's population live in areas with dirty air.